The three isotopes of hydrogen are hydrogen itself, deuterium and tritium (H.sub.2, D.sub.2 and T.sub.2 respectively). They find ever increasing use in industry and research and as a consequence there is an increasing interest in the sorption, storage and release of these gases in a safe and controlled manner.
Such sorption, storage and release (SSR) devices are well known in the art and have, for instance, been described by D. E. Soloman in U.S. Pat. No. 4,055,276. While they are capable of sorbing hydrogen isotopes at low pressures and on heating, releasing the isotope at a higher pressure it is often the case that this higher pressure is still many orders of magnitude below that which is desired. Furthermore, the pressure at which the isotope is released varies during isotope release due to changes of the concentration of sorbed isotope within the isotope sorption material (getter). This is due to the fact that for many traditional getter materials the hydrogen isotope equilibrium presure (p) (i.e. the hydrogen isotope pressure outside the getter material and the hydrogen isotope pressure within the getter material) is related to the concentration (q) of hydrogen isotope within the getter material and the getter material temperature (T) by a relationship of the form: ##EQU1## known as Sieverts' law.
Thus, whilst traditional hydrogen isotope sorption, storage and release (SSR) devices have the desirable feature of sorption at low isotope pressures they release the hydrogen isotope at pressures lower than those often required and even that pressure is not at a constant value but decreases drastically.
Materials which sorb hydrogen isotopes and release them at high pressures are also known. See for Example D. Shaltiel et al., Journal of the Less Common Metals, 53 (1977) 117-131. Nevertheless, such materials are not able to sorb significant quantities of hydrogen isotopes at low pressures. See also, U.S. Pat. Nos. 4,163,666 and 4,360,445.